Ardern is only the second prime minister in the world to give birth while in office - the first was Pakistan's Benazir Bhutto in 1990.

And in a beautiful twist of fate, the new First Baby of New Zealand shares her birthday with the late Bhutto.

Deputy Prime Minister Winston Peters is now looking after day-to-day activities in New Zealand while Ardern is on maternity leave for the next six weeks, but she will be on call for any major decisions.